1216509121 has 2 divisors, whose sum is σ = 1216509122. Its totient is φ = 1216509120.

The previous prime is 1216509113. The next prime is 1216509149. The reversal of 1216509121 is 1219056121.

It is an a-pointer prime, because the next prime (1216509149) can be obtained adding 1216509121 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 628204096 + 588305025 = 25064^2 + 24255^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216509121 - 2³ = 1216509113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1216509121.

It is not a weakly prime, because it can be changed into another prime (1216569121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608254560 + 608254561.

It is an arithmetic number, because the mean of its divisors is an integer number (608254561).

Almost surely, 2^1216509121 is an apocalyptic number.

It is an amenable number.

1216509121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216509121 is an equidigital number, since it uses as much as digits as its factorization.

1216509121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 28.

The square root of 1216509121 is about 34878.4908073730. The cubic root of 1216509121 is about 1067.5096013484.

The spelling of 1216509121 in words is "one billion, two hundred sixteen million, five hundred nine thousand, one hundred twenty-one".